The present invention relates to a flanged connector and base receptacle for receiving multiple cross sectional shapes and/or sizes of posts of the type used to support roadside signs. The base is readily attachable to a length of bare post using a simple mechanical attachment. The invention includes a system of providing a breakaway joint which is easily installed as a retrofit to existing solid posts with minimal modification of such a post the post. The invention also simplifies service of a post which has been damaged in use. It is particularly adaptable to use with breakaway sign post systems and allows solid sign posts to be readily retrofitted with a breakaway joint.